History

Rock County was created in 1836 as a territorial county on December 7, 1836 from
Milwaukee County and fully organized February 19, 1839.[3] The county is named for the
Rock River, which bisects the county from north to south.[4]

Geography

According to the
U.S. Census Bureau, the county has a total area of 726 square miles (1,880 km2), of which 718 square miles (1,860 km2) is land and 8.0 square miles (21 km2) (1.1%) is water.[5]

Cook Memorial Arboretum, a natural area with birding and nature trails, is located northwest of Janesville. It is owned by the
Janesville School District.[6]

There were 58,617 households out of which 33.60% had children under the age of 18 living with them, 53.50% were
married couples living together, 10.90% had a female householder with no husband present, and 31.10% were non-families. 25.10% of all households were made up of individuals and 9.70% had someone living alone who was 65 years of age or older. The average household size was 2.54 and the average family size was 3.03.

In the county, the population was spread out with 26.50% under the age of 18, 8.60% from 18 to 24, 29.80% from 25 to 44, 22.30% from 45 to 64, and 12.70% who were 65 years of age or older. The median age was 36 years. For every 100 females there were 97.00 males. For every 100 females age 18 and over, there were 94.10 males.